A tooth is comprised of an outer hard enamel protective layer and an inner dentin layer. The outer enamel layer is naturally either opaque white or slightly off-white in color. It is composed of apatite mineral crystals that are somewhat porous. Without being bound by theory, it is believed that the porous nature of the enamel layer permits staining agents and discoloring substances to permeate into the enamel and discolor a tooth.
Dentin, the inner bony part of the tooth, contains thousands of microscopic tubules. On the crown end of the tooth, the dentin tubule ends are normally sealed by the enamel. These dentin tubules pass all the way through the dentin from the enamel-sealed crown end to the pulp chamber. On the root end of the tooth, these tubules are also sealed by a bony material called cementum. However, if either the enamel-sealed crown ends or the cementum-sealed root ends of the dentin tubules become exposed, fluid easily travels through the tubules, causing hypersensitivity and/or pain. Undesirable exposure of dentin tubules may result from mechanical abrasion, caries, chemical treatment (e.g., whitening agents), and other factors.
Plaques are a major cause of both dental decay and inflammatory periodontal disease. These plaques can contain 250 or more separate microbial species. They use sugars and other fermentable carbohydrates to produce acids, which cause demineralization of the tooth surface, and polymers, with which the microbial organisms bind themselves to the tooth surface. In its initial stages, the formation of a carious lesion is not readily apparent. However, with prolonged and repeated demineralization by plaque-created acids, a cavity will ultimately become visible.
Peroxide has been used as an oxidizing agent for whitening teeth as well as for the treatment of various forms of stomatitis and gingivitis. See, e.g., U.S. Pat. No. 5,820,852. When applied for extended periods at high concentrations, oxidizing agents such as hydrogen peroxide and urea peroxide (carbamide) have proven effective for removing extrinsic and intrinsic stains as well as for brightening the overall shade and color of teeth. Unfortunately, the bleaching process for removing stains can simultaneously reduce the microhardness of enamel and dentin, cause post-treatment tooth sensitivity, and/or increase tooth susceptibility to demineralization. See Nathanson, D.; “Vital Tooth Bleaching: Sensitivity and Pulpal Considerations,” JADA, 128 (April 1997); and Attin, T. et aL, “Susceptibility of Enamel Surfaces to Demineralization after Application of Fluoridated Carbamide Peroxide Gels,” Caries Res. March-April; 37(2):93-9 (2003).
Various dental products have been formulated to address plaque formation and tooth whitening. For 5, U.S. Pat. No. 6,290,935 describes an oral composition comprising a peroxide first component (e.g., hydrogen peroxide, peroxydiphosphate, urea peroxide (carbamide), metal peroxides such as calcium peroxide, and salts of perborate, persilicate, perphosphate, and percarbonate) and a silicate clay activator second component, implanted with Fe ions. U.S. Pat. No. 6,521,215 describes compositions comprising a whitening agent comprising >10% peroxide (e.g., urea peroxide (carbamide) or hydrogen peroxide) and a soluble calcium phosphate remineralizing agent (e.g., monocalcium phosphate, anhydrous dicalcium phosphate, tricalcium phosphate, or tetracalcium phosphate). U.S. Pat. No. 6,419,905 describes a dental bleaching composition comprising urea peroxide (carbamide), xylitol, a potassium salt (e.g., potassium pyrophosphate or potassium phosphate), and a fluoride salt (e.g., sodium monofluorophosphate). U.S. Pat. No. 6,221,341 describes compositions for whitening teeth and/or having antimicrobial activity. These compositions comprise an acyl group (or functionally similar group) source or precursor and a peroxide source or precursor (e.g., urea peroxide (carbamide), sodium percarbonate, sodium perborate, calcium peroxide, magnesium peroxide, or sodium peroxide), which react in an aqueous environment to generate a peroxyacid (e.g., peroxyacetic acid). The compositions have a pH>5.2 to avoid solubilizing calcium in the tooth enamel or otherwise demineralizing the tooth. The peroxyacetic acid, which is unstable at this pH range, is therefore generated in situ by the above-described reaction. U.S. Pat. Nos. 6,102,050 and 5,967,155 describe dental flosses that administer various compounds to interproximal and subgingival dental areas for purposes such as whitening, remineralization, and desensitization. In addition to titanium dioxide as a whitening agent, other ingredients that may be incorporated into the floss include desensitizing agents (e.g., calcium nitrate, calcium hydroxide, or dibasic calcium phosphate), fluorides (e.g., calcium fluoride, sodium monofluorophosphate, aluminum mono- and di-fluorophosphate), peroxide compounds (e.g., calcium peroxide and sodium carbonate peroxide), and abrading agents (e.g., calcium). The fluoride compounds are taught to be catalytically active in remineralizing or precipitating calcium and phosphate compounds, found in saliva, onto teeth.
U.S. Pat. No. 5,902,568 describes compositions comprising hydrogen peroxide or a precursor (e.g., sodium perborate, persilicate, percarbonate, perphosphate, calcium peroxide, or sodium peroxide) and bicarbonate salt components that are separated from one another to prevent their premature reaction prior to use. The compositions have a pH range of 9-12, based on the combined components, to increase whitening. The hydrogen peroxide or precursor component may contain phosphoric acid. The bicarbonate salt component may contain a carbonate (e.g., calcium carbonate). In one or both of the peroxide or bicarbonate salt components, fluoride (e.g., stannous monofluorophosphate or sodium monofluorophosphate) may be present. U.S. Pat. No. 5,851,514 describes a whitening composition containing both a peroxide compound (e.g., calcium peroxide, hydrogen peroxide, urea peroxide (carbamide), glyceryl peroxide, or benzoyl peroxide) and an abrasive compound (e.g., dicalcium phosphate compounds such as dicalcium phosphate-dihydrate and anhydrous dicalcium phosphate or calcium pyrophosphate, preferably a high beta phase calcium pyrophosphate). U.S. Pat. No. 5,770,182 describes high viscosity sustained release dental compositions for treating tooth surfaces with whitening agents (e.g., urea peroxide) or fluorides (e.g., sodium fluoride). These components are included in a high viscosity matrix material (e.g., carboxypolymethylene) and are preferably applied using a dental tray.
U.S. Pat. No. 5,698,182 describes a composition for whitening teeth and inhibiting dental calculus comprising an anticalculus phosphate salt and calcium peroxide. U.S. Pat. No. 5,648,064 describes a two component dentifrice composition. The composition comprises a peroxygen compound first component (e.g., hydrogen peroxide, peroxydiphosphate, urea peroxide (carbamide), calcium, sodium, strontium, and magnesium peroxide salts, and perphosphate salts) and a manganese coordination complex (e.g., manganese gluconate) second component to activate the peroxygen compound and accelerate the release of active oxygen upon combining with the first component.
U.S. Pat. No. 5,624,906 describes an oral hygiene composition comprising a heteroatom containing alkyl aldonamide compound (e.g., alkoxymethyl gluconamide).
U.S. Pat. No. 6,303,104 describes a two-component composition for whitening and remineralizing teeth. The first component contains an at least partially soluble calcium salt, which may be a soluble calcium salt (e.g., calcium chloride, calcium bromide, calcium nitrate, calcium acetate, calcium gluconate, calcium benzoate, calcium glycerophosphate, calcium formate, calcium fumarate, calcium lactate, calcium butyrate, calcium isobutyrate, calcium malate, calcium maleate, calcium propionate, or calcium valerate) and optionally a soluble non-calcium divalent metal salt or an anhydrous calcium phosphate or dicalcium phosphate abrasive. The second component comprises a soluble orthophosphate salt (e.g., monopotassium phosphate) and optionally a fluoride salt (e.g., sodium monofluorophosphate). No peroxide is mentioned. U.S. Pat. Nos. 5,849,269; 5,820,852; and 5,776,437 describe oral compositions comprising a fluoride ion source (e.g., sodium monofluorophosphate), pyrophospate (e.g., tetrasodium pyrophosphate, either anhydrous salt or hydrated), and calcium peroxide. The oral compositions have a pH of 9.0-10.5.
U.S. Pat. No. 5,330,746 describes a composition containing either an anti-plaque agent (e.g., cetylpyridinium chloride) or an anti-hypersensitivity agent (e.g., a strontium salt). The agents are contained in a topically-applied varnish (e.g., a polymethacrylate) to provide their sustained release. The composition may also contain an oxygenating agent (e.g., urea peroxide (carbamide), hydrogen peroxide, peroxyborate, or peroxydiphosphate).
In view of these disclosures, there is an ongoing need in the art for compositions that can both whiten and remineralize teeth and fill voids associated with tooth decay and/or mechanical injury. Especially desired are compositions that comprise a whitening/stain removal agent (e.g., a source of peroxide and/or active oxygen) with sources of calcium ions and phosphate ions to remineralize teeth, thereby filling voids, adding strength, and reducing sensitivity.